Process for making cellulose acetate fibers

Abstract

A method for spinning a cellulose acetate fiber having a low degree of substitution per anhydroglucose unit (DS/AGU) of the cellulose acetate is provided. The addition of 5 to 40 weight percent water to cellulose acetate(CA)/acetone spinning solutions (dopes) will produce dopes that will allow fibers to be solvent spun using CA with a DS/AGU from 1.9 to 2.2.

I claim: 
     
       1. A method for the production of cellulose acetate fibers comprising (I) forming a solution consisting essentially of (a) about 10 to 40 weight percent, based on the total weight of (a), (b), and (c), of cellulose acetate having a DS/AGU of from 1.9 to 2.2;   (b) about 20 to 85 weight percent, based on the total weight of (a), (b), and (c), of acetone;   (c) about 5 to 40 weight percent, based on the total weight of (a), (b), and (c), of water; said solution having a zero shear viscosity at 29° C. of about 100 to about 10,000 poise;       (II) filtering said solution to form a spinning solution; followed by   (III) spinning said spinning solution at a temperature of about 25° C. to 95° C., at 200 to 1,500 meter/min. through spinnerette holes having a hole area equivalent to a circular diameter of 20 to 100 microns and length to diameter ratio of 0.5 to 3, thereby forming a cellulose acetate fiber having a dry linear density of 0.5 to 20 denier per filament and a total product denier of from 10,000 to 100,000 denier.   
     
     
       2. The method of claim 1, wherein the concentration of water is about 10 to about 40 weight percent, and the DS/AGU of the cellulose acetate is from about 1.9 to 2.1. 
     
     
       3. The method of claim 1, wherein the concentration of water is about 5 to about 35 weight percent and the DS/AGU of the cellulose acetate is from about 2.1 to 2.2. 
     
     
       4. The method of claim 1, wherein the concentration of water is about 10 to 15 weight percent. 
     
     
       5. The method of claim 1, wherein said solution has a zero shear viscosity at 29° C. of between about 200 and 4000 poise. 
     
     
       6. The method of claim 1, wherein said solution has a zero shear viscosity at 29° C. of between about 300 and 3000 poise.